Paradox of Stability of Nanoparticles at Very Low Ionic Strength

Lin, Shihong; Wiesner, Mark R.

doi:10.1021/la3016589

Cited by 21 publications

(20 citation statements)

References 58 publications

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“…Figure 6 presents calculated interaction energy profiles for the 20‐nm silica NP interacting with sand or biochar surface in NaCl and CaCl 2 solutions with different ISs. Although it is commonly reported that the interaction energy barrier decreases monotonically with increasing IS (Adamczyk and Weronski, 1999; Gregory, 1975; Hahn and O'Melia, 2004; Hahn et al, 2004; Ryan and Elimelech, 1996; Tosco et al, 2009), our calculations showed nonmonotonic variation of energy barrier with IS, similar to the theoretical results in Lin and Wiesner (2012). These theoretical calculations, however, deviate from the experimental result (i.e., monotonic increase of attachment with IS) reported in our study and in the literature (Bayat et al, 2015; Hahn and O'Melia, 2004; Hahn et al, 2004; Molnar et al, 2015; Yin et al, 2014).…”

Section: Resultssupporting

confidence: 87%

“…These theoretical calculations, however, deviate from the experimental result (i.e., monotonic increase of attachment with IS) reported in our study and in the literature (Bayat et al, 2015; Hahn and O'Melia, 2004; Hahn et al, 2004; Molnar et al, 2015; Yin et al, 2014). Lin and Wiesner (2012) demonstrated that the discrepancy is likely the reason that the equilibrium condition assumed in formulating the Possion–Boltzmann equation in the DLVO approach cannot be satisfied with fast moving NPs.…”

Section: Resultsmentioning

confidence: 99%

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Co‐transport of Pesticide Acetamiprid and Silica Nanoparticles in Biochar‐Amended Sand Porous Media

et al. 2016

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The role of biochar as a soil amendment on the transport of acetamiprid, a widely used neonicotinoid pesticide, is little known. We conducted saturated column experiments to examine cotransport of acetamiprid and silica nanoparticles (NPs) in pure and biochar-amended sands. Retention of acetamiprid was minor in the pure sand, whereas application of biochar in the sand significantly increased retention. Retention was greater at lower ionic strengths and near neutral pH values and was attributed to biodegradation and sorption through π-π interaction and pore filling. The convection-diffusion equation with inclusion of first-order sorption, desorption, and degradation well described the transport of acetamiprid in the biochar-amended sand. The simulation results show that the sorption rate did not change with pH. This is because the acetamiprid is nonionic and cannot be bonded with the biochar by protonation or deprotonation. The desorption rate was independent of variation of solution chemistry, indicating that desorption was a physical process (i.e., pore diffusion). Application of biochar in the sand had little influence on the transport of silica NPs in NaCl but caused complete attachment in CaCl. Energy dispersive X-ray spectroscopy suggested that the enhanced attachment was due to cation bridging between silica NPs and functional groups in biochar by the Ca. The co-presence of acetamiprid and silica NPs in the solutions enhanced transport of acetamiprid and NPs in the biochar-amended sand by competing for the binding sites on the biochar surfaces.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Co‐transport of Pesticide Acetamiprid and Silica Nanoparticles in Biochar‐Amended Sand Porous Media

et al. 2016

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“…Consequently, the theoretical calculations cannot explain the experimental observations. Lin and Wiesner (2012) obtained similar results for spherical nanoparticles by using the SEI technique to adequately evaluate the interaction energies. Conversely, if the Derjaguin approximation approach is used for the calculations, increasing IS will cause a decrease in the repulsive energy barrier (Hahn and O'Melia, 2004; Hahn et al, 2004; Shen et al, 2007, 2017; Torkzaban and Bradford, 2016).…”

Section: Resultsmentioning

confidence: 99%

Impact of Flow Velocity on Transport of Graphene Oxide Nanoparticles in Saturated Porous Media

Zhang¹,

Yan

Wang³

et al. 2018

Vadose Zone Journal

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Saturated column experiments were conducted to systematically examine transport of graphene oxide nanoparticles (GONPs) in sand porous media at different solution ionic strengths (ISs) with different flow velocities. Results show that deposition of GONPs increase with decreasing IS. However, the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy calculations using a surface element integration technique show that the energy barrier increases with increasing IS for the sheet-shaped colloids interacting with a planar sand surface. In contrast, the presence of nanoscale protruding asperities (NPAs) can cause a decrease in the energy barrier with increasing IS, which facilitates the attachment in primary minima at higher IS. At a given IS, increasing flow velocity increases attachment efficiency on the rough sand surfaces. Torque analysis shows that the maximum hydrodynamic torques are smaller than the adhesive torques, even for GONPs located on the NPAs where the adhesions are the lowest. Consequently, the attachment efficiency cannot be reduced by increasing flow velocity. Additional column experiments confirm that deposited GONPs cannot be detached by increasing flow velocity. Conversely, increase of flow velocity may enhance approaching of GONPs in low-flow regions such as concave areas of sand surfaces and subsequent attachment. Although it has been recognized in the literature that the presence of NPAs can cause decrease of attachment efficiency with increasing flow velocity for spherical colloids under both unfavorable and favorable chemical conditions, our results highlight a different role of surface roughness in attachment and detachment of sheet-shaped colloids under unfavorable conditions.

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“…One major problem is that the EDL interaction, which comprises both osmotic and Coulombic contributions [70,75], should theoretically have negligible impact on the overall interaction due to the very short Debye length (calculated to be $ 0.4 nm for the feed solution used). Within such a short Debye length, the vdW force should dominate the overall interaction and eclipse any difference in the EDL interaction.…”

Section: Mechanism Of Electrostatic Interactionmentioning

confidence: 99%

Tailoring surface charge and wetting property for robust oil-fouling mitigation in membrane distillation

Wang

Jin

Hou

et al. 2016

Journal of Membrane Science

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128

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a b s t r a c tThe efforts of developing anti-oil-fouling membranes have so far been focusing on tailoring membrane surface wetting properties, whereas the impacts of surface charge are often eclipsed. In this study, we investigated the impacts of surface charge and wetting property on oil fouling kinetics in membrane distillation (MD). Two composite membranes with in-air hydrophilic and underwater oleophobic surfaces, one of positive charge and the other of negative charge, were fabricated by modifying a hydrophobic polyvinylidene fluoride (PVDF) membrane with hydrophilic polyelectrolytes with different charges. The modified composite membranes were compared with the reference PVDF membrane for their contact angles, adhesion force curves, and fouling kinetics in MD processes. It was found that the negatively charged composite membrane performed the best in mitigating fouling by the negatively charged oil emulsion, followed by the positively charged composite membrane, with the pristine PVDF membrane being the most susceptible to oil fouling in MD experiments. The results from underwater oil CA measurements and oil probe force spectroscopy corroborated the results in the fouling experiments. The impact of surface charges on oil-membrane interaction and associated mechanism were also discussed.

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Paradox of Stability of Nanoparticles at Very Low Ionic Strength

Cited by 21 publications

References 58 publications

Co‐transport of Pesticide Acetamiprid and Silica Nanoparticles in Biochar‐Amended Sand Porous Media

Co‐transport of Pesticide Acetamiprid and Silica Nanoparticles in Biochar‐Amended Sand Porous Media

Impact of Flow Velocity on Transport of Graphene Oxide Nanoparticles in Saturated Porous Media

Tailoring surface charge and wetting property for robust oil-fouling mitigation in membrane distillation

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